OPA1632

SBOS286A − DECEMBER 2003 − REVISED SEPTEMBER 2006

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The PowerPAD package allows for both assembly and

thermal management in one manufacturing operation.

During the surface-mount solder operation (when the

leads are being soldered), the thermal pad must be

soldered to a copper area underneath the package.

Through the use of thermal paths within this copper

area, heat can be conducted away from the package

into either a ground plane or other heat-dissipating

device. Soldering the PowerPAD to the printed circuit

board (PCB) is always required, even with applications

that have low power dissipation. It provides the

necessary

thermal

and

mechanical

connection

between the lead frame die pad and the PCB.

PowerPAD PCB LAYOUT CONSIDERATIONS

1.

The thermal pad must be connected to the most

negative supply voltage on the device, V−.

2.

Prepare the PCB with a top-side etch pattern, as

shown in Figure 4. There should be etch for the

leads as well as etch for the thermal pad.

68mils x 70mils

(via diameter = 13mils)

Single or Dual

Figure 4. PowerPAD PCB Etch and Via Pattern.

3.

Place five holes in the area of the thermal pad.

These holes should be 13mils in diameter. Keep

them small so that solder wicking through the holes

is not a problem during reflow.

4.

Additional vias may be placed anywhere along the

thermal plane outside of the thermal pad area.

These vias help dissipate the heat generated by the

OPA1632 IC, and may be larger than the 13mil

diameter vias directly under the thermal pad. They

can be larger because they are not in the thermal

pad area to be soldered so that wicking is not a

problem.

5.

Connect all holes to the internal power plane that is

at the same voltage potential as V−.

6.

When connecting these holes to the plane, do not

use the typical web or spoke via connection

methodology. Web connections have a high

thermal resistance connection that is useful for

slowing

the

heat

transfer

during

soldering

operations. This makes the soldering of vias that

have plane connections easier. In this application,

however, low thermal resistance is desired for the

most efficient heat transfer. Therefore, the holes

under the OPA1632 PowerPAD package should

make their connection to the internal plane with a

complete

connection

around

the

entire

circumference of the plated-through hole.

7.

The top-side solder mask should leave the terminals

of the package and the thermal pad area with its five

holes exposed. The bottom-side solder mask should

cover the five holes of the thermal pad area. This

prevents solder from being pulled away from the

thermal pad area during the reflow process.

8.

Apply solder paste to the exposed thermal-pad

area and all of the IC terminals.

9.

With these preparatory steps in place, the IC is

simply placed in position and runs through the

solder

reflow

operation

as

any

standard

surface-mount component. This results in a part

that is properly installed.